In various kinds of machines such as industrial robots, it is conventionally known to control the operating position and orientation of a machine operating section, e.g., a robot hand, in dependence on the position of a work object, which is detected by a visual sensor system, to thereby effect required work. Typically, in this case, an image of a single sample object is analyzed to prepare taught data (model) for image processing, which is to be supplied beforehand to a visual sensor. Then, to recognize the position of the work object, the taught data is compared with an image (scene) of the work object photographed by a camera of the visual sensor system. Conventionally, a manual modification of the taught data is carried out in a trial-and-error manner, so long as instability is found in the work object recognition based on the taught data. This taught data modification requires skill and labor.